The results quantify the broad popularity of expanding background checks on firearms purchases across the political spectrum, even among a segment of the public usually opposed to gun-control measures. Support for universal background checks ranges from mild among Republican men to strong among Republican women to almost wild among Democrats.

Three-quarters of Democrats said they would be "very pleased" to see background-check legislation enacted—more than the 64 percent of Republicans who said they would be "very pleased" if the Affordable Care Act, also known as Obamacare, was repealed.

At first glance, the political downside to background-check legislation is virtually nonexistent: Just 14 percent of all Americans and just 19 percent of Republicans said they would be "very disappointed" if such a law was enacted. Among Republican women, just 12 percent said the same.

However, 30 percent of Republican men said they would be "very disappointed" if universal background checks became law. That finding helps to explain the fate of the background-check legislation sponsored by Sens. Pat Toomey, R-Pa., and Joe Manchin, D-W.Va., last April, and illustrate the ability of a vocal minority to scuttle legislation that most Americans support. Despite the issue's national appeal, Toomey and Manchin's amendment to expand background checks to gun shows and Internet sales was opposed by four Senate Democrats and attracted the support of only four Republicans, thus failing to reach the 60 votes needed to avoid a filibuster.